NASA Technical Reports Server (NTRS) 20160000579: The Human Factors of an Early Space Accident: Flight 3-65 of the X-15

Human Systems

integration division

The Human Factors of an Early Space
Accident: Flight 3-65 of the X-15

Immanuel Barshi, NASA Ames Research Center
Irving C. Statler, NASA, Ames Associate (retired)

With Jeb S. Orr, The Charles Stark Draper Laboratory, Inc.

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USAF Major Michael J. Adams

Report of the Air Force-NASA
Accident Investigation Board

Human Systems

integration division

NASA FLIGHT RESEARCH CENTER

INVESTIGATION OF THE CRASH OF THE
X-15-3 AIRCRAFT ON NOVEMBER 15, 1967

Testimony of Air Force witnesses was
taken under A F Reg. t 21-4 and special
handling is required. The statements
of these witnesses must be removed before
transmittal of the document to nongovernment

JANUARY 1968
EDWARDS, CALIFORNIA

Notice

agencies or persons.

3

The Highly Successful X-15 Research Program

• X-15 Program (1959 - 1968)

- Experimental rocket-powered research vehicle

- Research of all aspects of piloted hypersonic flight (especially altitude
& speed)

Achieved:

* 199 flights

❖ 4,519 mph (Mach 6.7)

* 354,200 ft (> 67 mi)

Some flights qualified as space flights

♦> 13 flights exceeded AF criterion

❖ 2 flights exceeded FAI criterion

Data contributed to Projects Mercury, Gemini, & Apollo as well as Space
Shuttle

The X-15 Hypersonic Research Aircraft

Hydrogen

peroxide

YLR-99

Anhydrous ammonia
tank (fuel)

Liquid oxygen
tank (oxidizer)

Liquid nitrogen

Auxiliary
power units

Attitude

Hydrogen

peroxide

tanks

Ejection seat

5

Launch of the X-15 from the B-52

TYPICAL X-I5 RESEARCH MISSION

Slide Courtesy of X-15 Pilot Astronaut Bill Dana

7

The X-15-3

• Three different X-15 models were produced.

• All three relied on a Stability Augmentation System - the first 2
models had pilot-selectable control gains.

• The MH-96 Adaptive Flight Control System was unique to the
X-15-3 - provided automated gain control and automated
engagement of reaction controls.

• Pilot's display in X-15-3 was importantly different from first 2
models.

8

The Attitude Director Indicator in the X-15-3

Selection switch and
indicator light for PAI

Attitude Director Indicator

IFDS malfunction

Pilot's Display Panel in the X-15-3

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The MH-96 Adaptive Flight Control System

On X-15-3, the MH-96 AFCS was intended to provide:

‘Automatic control of the gain of inputs to the
aerodynamic control surfaces in all three axes as a
function of dynamic pressure

‘Automatic engage/disengage of the reaction controls

‘Ability to use the right side stick for both aerodynamic
and reaction controls

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Configuration of X-15-3 and Plan for Flight 3-65

■ 65 th flight of the X-15-3.

■ A high altitude flight -max altitude ~ 250,000 feet.

■ Flight plan and configuration similar to previous two
X-15-3 flights.

■ Flight 3-65 had a full schedule of maneuvers and
experiments including:

bow-shock standoff measurement,
solar-spectrum measurements,
ultraviolet exhaust-plume measurements, and
micrometeorite collection.

■ Differences in configuration of the X-15-3 for Flight
3-65 included a traversing probe installed in the pod
of its right wingtip that was operated for the first
time in a high-altitude flight.

12

The Wing-tip Pod for Experiment Installation

Typical X-15 Altitude Mission

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Key Events During Flight 3-65

10:30:07 - Launched from B-52 at 45,000 ft. altitude with all systems
operating normally, the pilot ignited the boost rocket, and the X-15-3
accelerated into a steep climb.

10:31:07 - at about 90,000’, arcing from the motor drive of the traversing
probe caused an electrical disturbance to the aircraft’s electrical system that
continued until 10:33:53. Noise begins in all telemetered data channels.

10:31:28 - Major Adams reported IFDS computer- and the instrument-
malfunction lights. Ground Control acknowledged report. (& 10:31:58)

10:31:34 - Pilot switched ADI to PAI mode and switched source of data for
a and (3 as well as for altitude and velocity from the nose ball to IFDS and
IMU (while the malfunction lights were still on).

10:31:40 to 10:32:00 - Executed wing-rock maneuver; exceeded specified
bank angles started a slow yaw drift to the right.

10:32:08 to 10:32:23 - Executed the computed a/p-check maneuver.

10:32:50 - Initiated the Precision Attitude-Tracking Task

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Key Events During Flight 3-65 (continued)

10 : 32:51 - The Flight Controller reported to pilot, “Over the top at about 261

10 : 33:01 - The Flight Controller told the pilot that he was looking “real
good”.

10 : 33:05 - The pilot switched to direct control of the RCS using the left side
stick. Major Adams continued to try to complete execution of the precision
attitude-tracking task.

10 : 33:25 - The Flight Controller once again assured the pilot that he was “a
little bit high, ” but in “real good shape. ”

10 : 33:39 - The pilot reported that the aircraft control seemed "squirrelly. ”

10 : 34:01 - Major Adams said, “I’m in a spin. ” (& 10:34:16; 10:34:19)

10 : 34:30 - After three revolutions, the aircraft came out of the spin and went
into a 45 -degree inverted dive.

10 : 34:37 - the MH-96 AFCS entered into a limit-cycle instability forcing
control surfaces into rapid, cyclic oscillation to their limit of travel at their
maximum rate of 26° per second.

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10:34:54 - The aircraft began to break up.

10:34:58 - The largest pieces impacted the ground

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Time Line of Critical Events Prior to Spin

Time

80

143

210 253

Approximate Altitude (in thousands of feet)

265

250

208

K

Approximately 3 Minutes

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Time History of MH-96 Gains During Flight 3-65

Altitude
x 1000 ft

Pitch gain

(percent of maximum)

Roll gain

(percent of maximum)

Yaw gain

(percent of maximum)

10 : 31:00

10 : 32:00

10 : 33:00

10 : 34:00

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Time history Telemetered Parameters of Flight 3-65

Inertial and
Radar Altitude
X 1000 ft.

Inertial and
Radar Velocity
X 1000 ft/sec

T/M Pitch
Attitude
dog.

T/M Angle
of Attack
deg.

T/M Horan!
Acceleration
S

T/M Boll
Attitude
deg.

ieo-i

90-

T/K Angle of
Sideslip and
Heading

3(58 • ™

270-

180 -

T/M Long.
Acceleration
S

10:30:00 10:31:00 10:32:00 10:33:00 10:34:00 10:35:00

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Causal Factors of the X-15-3 Accident

A Latent Causal Factor of the Flight 3-65 accident was
management’s failure to require environmental testing of
experimental equipment before it was installed on the aircraft
(equipment not considered “flight critical”).

A Proximate Causal Factor was the confluence of the failures of

1 . the aircraft system design and

2. ground control

to alert the pilot to the possibility of control problems and
erroneous data when indications of malfunctions were observed.

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Ground's evidence of problems

> At 10:31:07 (just 1 minute after launch), all of the telemetered data
suddenly became erratic and remained so for several minutes .

> Starting at 10:31:07, the telemetered data on altitude and velocity
differed from the radar data and was noted by a ground controller.

> At 10:31:58, the Flight Controller acknowledged the pilot's report that the
IFDS computer and instrument malfunction lights were on.

> Between 10:31:40 and 10:32:00, during the wing-rock maneuver, a
member of ground control reported to the Flight Controller that the pilot
was having a control problem based on his observations of larger than
normal pitch-roll servo excursions.

> At 10:32:26, disengagement of the pitch and roll dampers was reported
by the pilot and acknowledged by the Flight Controller.

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Key Flight Control Transmissions During Flight 3-65

10:31:07 - Evidence of problems
10:31:13 - “Okay, right on track. ”

10:31:21 - “On profile, on heading. ”

10:31:45 - “Rock your wings and extend your experiment, Mike. ”
10:31:50 - “On heading, on profile. ”

10:31:58 - Pilot reports Tve got a computer and instrument light! ”
10:32:14 - “Check your computed a now. ”

10:32:19 - “Right on the track. ”

10:32:28 - Pilot reports “I lost my Pitch & Roll Dampers! ”

10:32:43 - “You are looking real good, right on the heading, Mike. ”
10:33:01 - “Your heading is going in the right direction, Mike, real good. ”
10:33:25 - “A little bit high, Mike, but real good shape. ”

10:34:01 - Pilot reports “I am in a spin! ”

10:34:03 - “Lets get your experiment in and the camera on. ”

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Contributing Factors to the X-15-3 Accident

1. The MH-96 AFCS had a known tendency to go into limit-cycle oscillations
when the system was operating at or close to maximum gain.

2. The design of the adaptive gain control in the MH-96 allowed a failure in
the AFCS to interfere with the pilot’s ability to control the aircraft.

3. The pilot’s display used a single critical instrument, the Attitude Director
Indicator, in two different modes; one a normal mode used most of the time,
the other a mode (Precision Attitude Indicator) that was used only
occasionally.

4. There was no provision for backup source of reliable information for the
pilot at high altitude when the IFDS computer malfunctioned.

5. A speculation in the AIB report and elsewhere was that Major Adams’
susceptibility to Type II Spatial Disorientation was a Contributing Factor in the
scenario of this accident.

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Contributing Factors to the X-15-3 Accident (cont.)

6. Major Adams did not correct the error in yaw when he switched to direct
control of the RCS through the left side stick.

7. Evidence suggests that Major Adams’ responses to the PAI were consistent
with an ADI mode when he switched to the left-hand stick control of the RCS.

8. Evidence indicates that Major Adams forgot to disengage the MH-96 AFCS
as he was supposed to when he switched to the left side stick control.

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Conclusions

Human Systems

integration division

1 . The electrical disturbance due to arcing of unqualified experimental

equipment precipitated the accident.

2. The pilot had no reliable control during the electrical disturbance.

3. The pilot was, very likely, unable to recognize the control problems.

4. Flight 3-65 would have very likely been recoverable, if ground control had
aborted the mission when they had clear indications of malfunctions.

5. The focus of Major Adam’s attention on performing the precise wing-rock
maneuver using an intermittent RCS may have distracted him from noticing
the yaw angle acquired during the boost phase.

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Conclusions (cont.)

Human Systems

integration division

6. There was no evidence that Spatial Disorientation degraded Major Adam’s
performance during the boost phase or the execution of the experimental
maneuvers.

7. The pilot’s ability to manage the aircraft’s various malfunctions when he
switched to direct control was affected by an extremely high workload.

8. The limit-cycle oscillations of controls would have probably been prevented
had Major Adams disengaged the MH-96 AFCS when he switched to manual
control.

9. The destruction of the X-15-3 was due to the structural loads produced by
the high frequency limit-cycle oscillations of the control surfaces induced by
the AFCS.

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Human Systems

integration division

Thank you!

NASA/TM-2014-2 18538
NESC-RP-14-00957

A Comprehensive Analysis of the X-15
Flight 3-65 Accident

Cornelius J. Dennehy /NESC

Langley Research Center, Hampton, Virginia

JebS. On-

Draper Laboratory, Huntsville, Alabama

Immanuel Barshi, and Irving C. Statler
Ames Research Center, Moffet Field, California

http://hsi.arc.nasa.gov/awards pubs /
publication view.php?publication id=2378

October 2014

N AS A/TM— 20 1 4-2 1 84 1 4

The Human Factors of an Early Space Accident:

Flight 3-65 of the X-15

Immanuel Barshi

NASA Ames Research Center

Irving C. Statler

NASA Ames Research Center

http://hsi.arc.nasa.gov/awards pubs /
publication view.php?publication id=237]

June 2014

For questions, contact me at: Immanuel. Barshi@nasa.gov

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